With the rapid development of smart phones, more and more mobile communication terminals are integrated with wireless local area network (WLAN, Wireless Local Area Network) communication modules, such as WiFi (Wireless Fidelity, wireless fidelity) modules. On the other hand, with constant increase of requirements of people on the mobile broadband, the current wireless cell communication system bears the increasingly greater pressure of data traffic. In a feasible method, the wireless cell technology and the WLAN technology are integrated into each other, and a WLAN is used to divert part of data traffic of a mobile cell communication system, thereby greatly improving user experience of a cellular system.
Many solutions are available for integrating a cellular network with a WLAN, and the simplest one is an independent WLAN networking solution characterized by AP (access point, Access Point)+AC (AP controller, AP Controller). An AP is an access point of a WLAN. After an association and authorization process, a WLAN terminal may communicate with the AP. An AC has functions of routing and switching as well as managing the AP. An external interface of the AP is an IP interface. Therefore, through the AC, a user IP data packet from the AP may enter an external IP packet network, typically the Internet (the Internet). In order to perform authentication, authorization, and accounting on a user, the AC is connected to an AAA server (authentication, authorization and accounting; Authentication, Authorization and Accounting). Normally, the user accesses a WLAN network by inputting an account name and a password provided by an operator. Alternatively, a 3GPP AAA server in a mobile communication network, such as GPRS, UMTS or LTE, of a mobile operator performs authentication, authorization, and accounting. The 3GPP AAA server is connected to an HLR (Home Location Register, home location register). In this way, manual operations, such as inputting an account name and a password, are not required, instead, a mobile phone uses user subscription information stored in a SIM (Subscriber Identity Module, subscriber identity module) card or a USIM (Universal Subscriber Identity Module, universal subscriber identity module) card to automatically perform authentication and authorization operations of the user, thereby greatly simplifying and facilitating use of the WLAN network by the user.
Although the networking solution of an independent WLAN is simple, the networking solution supports neither interworking with the mobile communication network nor reuse of existing devices in the mobile communication network such as GPRS, UMTS, or LTE. The interworking not supported includes: handover between the WLAN and the mobile communication network, and accessing a PS (Packet-Switched Domain, packet-switched domain) service such as an IMS (IP Multimedia Subsystem, IP multimedia subsystem) service through the WLAN. The unlicensed spectrum used by the WLAN is vulnerable to different types of interference, and the WLAN AP is generally set up in hotspot areas, instead of being networked to provide continuous coverage. Therefore, when the WLAN is unavailable due to interference, or, when the UE leaves the coverage area of the AP, it is very important to hand over the UE to a mobile communication network such as GPRS, UMTS, or LTE. Therefore, an I-WLAN (Interworking WLAN, interworking WLAN) networking manner of 3GPP may be used.
Taking GPRS and UMTS systems as an example, an AC is connected to a GGSN (Gateway GPRS Support Node, gateway GPRS support node) through a TTG (Tunnel Terminating Gateway, tunnel terminating gateway). The GGSN is a gateway between the GPRS and UMTS systems and an external IP network, and the TTG is connected to the GGSN through a standard Gn interface of the 3GPP. In this way, the WLAN is connected with the GGSN through the TTG to implement interworking with the mobile communication network such as GPRS, UMTS, or LTE and reuse the existing functions of the mobile communication network such as authentication, authorization, accounting, policy control/traffic policing. Alternatively, a TG function and a GGSN function may be combined into a PDG (Packet Data Gateway, packet data gateway).
Based on the I-WLAN manner, the 3GPP further proposes IFOM (IP Flow Mobility and Seamless WLAN Offloading, IP flow mobility and seamless WLAN offloading) in Release 10, so as to further improve user experience, which is mainly characterized in that a UE (User Equipment, user equipment) is allowed to use a mobile communication network, such as GPRS, UMTS, or LTE, and an I-WLAN network to transmit different IP data streams of the UE, thereby realizing more flexible data offloading and increasing a peak rate of a user.
For the independent WLAN and I-WLAN, the existing WLAN networking modes have a common characteristic that the WLAN is a completely independent network. Therefore, mobile operators who have no fixed network resources need to construct a new transmission network for the WLAN, which increases the period and cost of network construction.